Two dimensional and three dimensional displays are well known to be made monochromatic displays. However, monochromatic does not offer the detail such as shown using red, green and blue colors. Displays using liquid crystals have been proposed of generating color displays. A problem with this type of prior art display is that they require arranging individual pixels in rows and corresponding columns. Another problem is that the devices described can be expensive and complicated to manufacture, can have a narrow angular view ranges with low brightness.
Several patents have been proposed for panel displays using two-frequency up conversion fluorescence. For example, U.S. Pat. Nos. 5,684,621; 5,764,403; 5,914,807; 5,943,160; and 5,956,172 all issued to Downing. The Downing '403 patent appears to be the most relevant to the subject invention. Downing '403 is primarily concerned with embodiments where the use different layers for red, green and blue emitters briefly describes some mixing in mixing of only crystal type materials in a single display media. However, for the single display media, Downing '403 uses nanometer sized particles which would inherently be difficult to form, handle and disperse in a display medium.
U.S. Pat. No. 6,327,074 titled “Display media using emitting particles dispersed in a transparent host” issued to M. Bass and H. Jenssen on Dec. 4, 2001 discloses two and three dimensional color image displays. The displays include a display medium having a substantially uniform dispersion of red, green and blue visible light emitting particles sized between approximately 0.5 to approximately 50 microns therethrough. The particles can be dye doped polymethylmethacrylate(pmma) plastic, and the display medium can be pmma, acrylic plastic or glass. Other particles can be used such as rare earth doped crystals. The two dimensional display uses three laser sources each having different wavelengths that direct light beams to each of three different types of particle in the display medium. Light is absorbed by the particles which then become excited and emit visible fluorescence. Modulators, scanners and lens can be used to move and focus the laser beams to different pixels in order to form the two dimensional images having different visible colors.
U.S. Pat. No. 6,501,590 titled “Display medium using emitting particles dispersed in a transparent host” issued to M. Bass and H. Jenssen on Dec. 31, 2002 describes another two and three dimensional color image display device. The displays include a display medium having a substantially uniform dispersion of red, green and blue visible light emitting particles sized between approximately 0.5 to approximately 50 microns therethrough. The particles can be dye doped polymethylmethacrylate(pmma) plastic, and the display medium can be pmma, acrylic plastic or glass. Other particles can be used such as rare earth doped crystals. The two dimensional display uses three laser sources each having different wavelengths that direct light beams to each of three different types of particle in the display medium. Light is absorbed by the particles which then become excited and emit visible fluorescence. Modulators, scanners and lens can be used to move and focus the laser beams to different pixels in order to form the two dimensional images having different visible colors.
Two and three dimensional display based on up conversion of near infrared light to the visible are described in U.S. Pat. No. 6,654,161 titled “Dispersed crystallite up-conversion displays” issued to M. Bass, H. Jenssen and Alexandra Rapaport issued on Nov. 25, 2003. The display medium is a transparent polymer containing particles of crystals doped with Yb.sup.3+ and other rare earth ions. The Yb.sup.3+ ions absorb light from a commercially available diode laser emitting near 975 nm and transfer that energy to the other dopant ions. Using a fluoride crystal host, NaYF.sub.4, co-doped with Tm.sup.3+ ions we obtain blue light at .about.480 nm, with Ho.sup.3+ or Er.sup.3+ ions we obtain green light at .about.550 nm and with Er.sup.3+ we obtain red light at .about.660 nm. The display medium is also used with a preferred component layout with experimentation test data, along with applications for full color, high brightness, high resolution, displays.
The doping of heavy metal luminophores in commercially available optical grade plastics, such as poly (methyl methacrylate) or polystyrene, generally results in the aggregation of the metal salt. This aggregation leads to excessive light scattering, weakening of the plastic's mechanical strength, and an inhomogenous composite that would be unsuitable for optical or display applications. U.S. Pat. No. 6,844,387 titled “Composites of inorganic luminophores stabilized in polymer hosts” issued to M. Bass and K. Belfield issued on Jan. 18, 2005 discloses a two and three dimensional display medium having a novel transparent polymer composite containing particles of crystals doped with Yb.sup.3+ and other rare earth ions. The polymer composite creates homogeneously dispersed compositions without cracking or delamination of the film and can be used for various optical applications.
U.S. Pat. No. 6,897,999 titled “Optically Written Display” issued to Jason Eichenholz, M. Bass and Alexandra Rapaport issued on May 25, 2005 discloses another two, three dimensional color displays having uniform dispersion of red, green and blue visible light emitting micron particles. Pumping at approximately 976 nm can generate green and red colors having an approximately 4% limit efficiency. Modulators, scanners and lens can move and focus laser beams to different pixels forming two dimensional color images. Displays can be formed from near infrared source beams that are simultaneously split and modulated with micro electro mechanical systems, spatial light modulators, liquid crystal displays, digital micromirrors, digital light projectors, grating light valves, liquid crystal silicon devices, polysilicon LCDs, electron beam written SLMs, and electrically switchable bragg gratings. Pixels containing: Yb,Tm:YLF can emit blue light, Yb,Er(NYF) can emit green light, and Yb,Er:KYF and Yb,Ef:YF.sub.3 can emit red light.
U.S. Pat. No. 5,089,860 issued to D. G. Deppe and T. J. Rogers and titled “Quantum Well Device With Control of Spontaneous Photon Emission, and Method of Manufacturing Same,” on 18 Feb. 1992 describes spontaneous photon emission intensity in a semiconductor quantum well that is strongly influenced by a highly reflecting interface, with the quantum well to interface spacing being less than the optical emission wavelength of the quantum well. An enhancement/inhibition ratio on the order of 10 is possible according to the present invention using a single reflector, and enhancement/inhibition ratios on the order of 1000 are possible when two reflectors are used in the quantum well light-emitting diode structures. In addition, according to the present invention, the gain, directionality, and efficiency of a vertical cavity surface-emitting laser can also be greatly improved. The patent includes a method of making the spontaneous photon emission intensity in a semiconductor quantum well.
A recent patent related to the subject matter of the present invention issued on Dec. 30, 2008 to the same assignee as the subject application and having a common inventor with the subject application is U.S. Pat. No. 7,471,706. The patent discloses a light emitting device that includes a substrate, at least one semiconductor light emitting device formed in or on the substrate, and up converting material disposed in or on the substrate. The up converting material is disposed in a path of light processed or emitted by the semiconductor device. The up converting material absorbs light emitted by the semiconductor device and emits up converted light in response. Integrated pixelated displays include a plurality of pixels formed on a surface of the substrate, with each pixel including up-conversion material based red light source, a blue light source a green light source, and a structure for selectively controlling emission from the red, blue and green lights sources for each of the pixels.
The methods and systems of the present invention provides a system using up converters in combinations with semiconductor light sources capable of producing the red, green and blue light needed to make a full color display with an extremely large color gamut. However, the efficient red emitter, 1% Er, 18% Yb:YF3, emits some green light simultaneously with the red light making it appear yellow to the eye. The efficient green emitter, 1% Er, 18% Yb:NaYF, emits some red light while simultaneously emitting green though the eye is so sensitive to green that the red is only seen at the edges of the green up converting emitter. The efficient blue emitter, 0.4% Tm, 20% Yb:KY3F10, emits some red light when it emits blue and thus looks purple to the eye. The problem of multiple colors of emission that applies to the specified up converters, also exists for other up converters.
What is needed overcome the problem with prior art up conversion display systems is a solution based on properly designed optical thin film coatings that enables color separation to produce only the selected red, green and blue wavelength light from the up converters to be delivered by the display.